As yet it is unclear whether Thanos will be the main villain in both movies, but his status as one of Marvel's non-Earth-based characters appears to make him a good fit for the cosmic focus of the Guardians of the Galaxy film.

In the Marvel universe, Thanos is a mutant from the moon Titan, and is descended from the superhuman race of Eternals. His servitude and love for Mistress Death leads to him raining death and destruction across the Marvel universe in an attempt to win her affection.

Guardians of the Galaxy is set for release on August 1, 2014, with The Avengers 2 set for a May 2015 release date.